The secretory response of the rat anterior pituitary to gonadotropic hormone releasing hromone (LHRH) in vivo varies with the stage of the estrous cycle or hormonal background; further LHRH has a self-potentiating or priming effect on the release of the gonadotropins. The cellular mechanisms involved in the release of gonadotropins following LHRH stimulation are unknown. There is a Ca ion requirement for LHRH-induced gonadotropin release from the anterior pituitary, but the site of Ca ion involvement is not clear although in this and other tissues a change in intracellular Ca ion activity is thought to occur following stimulation. Cyclic nucleotides are also reported to be involved in gonadotropin secretion; disparate reports of the relative contributions of adenosine 3',5'-monophosphate (cAMP) and guanine 3',5'-monophosphate (cGMP) in the secretory prosess are attributable in part to sexual differences. The present study will examine gonadotropin secretion from isolated anterior pituitaries from cycling female rats in a continuous flow, superfusion system in vitro. The aim is to characterize the roles of Ca ions and other inorganic ions and of cAMP and cGMP in gonadotropin secretion; the interaction of these factors will also be analyzed. The self-priming response to LHRH will be used as a model to study the components of the system. Following stimulation with either single or multiple pulses of LHRH at various cycle stages, changes in gonadotropin secretion will be correlated with changes in fractional Ca ions efflux taken as a measure of intracellular Ca ions activity changes. In addition, tissue and effluent from the superfusion incubation will be assayed for cAMP and cGMP concentration. The ionic and cyclic nucleotide environment of the tissue will be manipulated to examine further their role in gonadotropin secretion. The ultimate objective of these studies is to identify the sites and sequence of involvement of Ca ions and cyclic nucleotides in the chain of events initiated by the interaction of LHRH and its receptor which ultimately results in gonadotropin secretion.